Class ValueComparison

    • Constructor Detail

      • ValueComparison

        public ValueComparison​(Expression p1,
                               int op,
                               Expression p2)
        Create a comparison expression identifying the two operands and the operator
        Parameters:
        p1 - the left-hand operand
        op - the operator, as a token returned by the Tokenizer (e.g. Token.LT)
        p2 - the right-hand operand
    • Method Detail

      • getExpressionName

        public java.lang.String getExpressionName()
        Get a name identifying the kind of expression, in terms meaningful to a user.
        Overrides:
        getExpressionName in class Expression
        Returns:
        a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.
      • getAtomicComparer

        public AtomicComparer getAtomicComparer()
        Get the AtomicComparer used to compare atomic values. This encapsulates any collation that is used. Note that the comparer is always known at compile time.
        Specified by:
        getAtomicComparer in interface ComparisonExpression
        Returns:
        the comparer
      • getStringCollator

        public StringCollator getStringCollator()
        Get the StringCollator used to compare string values.
        Specified by:
        getStringCollator in interface ComparisonExpression
        Returns:
        the collator. May return null if the expression will never be used to compare strings
      • getSingletonOperator

        public int getSingletonOperator()
        Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT, Token.FLE, Token.FGE
        Specified by:
        getSingletonOperator in interface ComparisonExpression
        Returns:
        the operator, as defined in class Token
      • convertsUntypedToOther

        public boolean convertsUntypedToOther()
        Determine whether untyped atomic values should be converted to the type of the other operand
        Specified by:
        convertsUntypedToOther in interface ComparisonExpression
        Returns:
        true if untyped values should be converted to the type of the other operand, false if they should be converted to strings.
      • setResultWhenEmpty

        public void setResultWhenEmpty​(BooleanValue value)
        Set the result to be returned if one of the operands is an empty sequence
        Parameters:
        value - the result to be returned if an operand is empty. Supply null to mean the empty sequence.
      • getResultWhenEmpty

        public BooleanValue getResultWhenEmpty()
        Get the result to be returned if one of the operands is an empty sequence
        Returns:
        BooleanValue.TRUE, BooleanValue.FALSE, or null (meaning the empty sequence)
      • needsRuntimeComparabilityCheck

        public boolean needsRuntimeComparabilityCheck()
        Determine whether a run-time check is needed to check that the types of the arguments are comparable
        Returns:
        true if a run-time check is needed
      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                                    ContextItemStaticInfo contextInfo)
                             throws XPathException
        Type-check the expression
        Overrides:
        typeCheck in class BinaryExpression
        Parameters:
        visitor - an expression visitor
        contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
        Returns:
        the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)
      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                                   ContextItemStaticInfo contextInfo)
                            throws XPathException
        Perform optimisation of an expression and its subexpressions.

        This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

        Overrides:
        optimize in class BinaryExpression
        Parameters:
        visitor - an expression visitor
        contextInfo - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
        Returns:
        the original expression, rewritten if appropriate to optimize execution
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)
      • isNegatable

        public boolean isNegatable​(TypeHierarchy th)
        Check whether this specific instance of the expression is negatable
        Specified by:
        isNegatable in interface Negatable
        Parameters:
        th - the type hierarchy
        Returns:
        true if it is
      • negate

        public Expression negate()
        Return the negation of this value comparison: that is, a value comparison that returns true() if and only if the original returns false(). The result must be the same as not(this) even in the case where one of the operands is ().
        Specified by:
        negate in interface Negatable
        Returns:
        the inverted comparison
      • equals

        public boolean equals​(java.lang.Object other)
        Description copied from class: BinaryExpression
        Is this expression the same as another expression?
        Overrides:
        equals in class BinaryExpression
        Parameters:
        other - the other operand; the result is false if this is not an Expression
        Returns:
        true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.
      • computeHashCode

        protected int computeHashCode()
        Get a hashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.
        Overrides:
        computeHashCode in class BinaryExpression
        Returns:
        a computed hash code
      • copy

        public Expression copy​(RebindingMap rebindings)
        Copy an expression. This makes a deep copy.
        Specified by:
        copy in class Expression
        Parameters:
        rebindings - variables that need to be re-bound
        Returns:
        the copy of the original expression
      • effectiveBooleanValue

        public boolean effectiveBooleanValue​(XPathContext context)
                                      throws XPathException
        Evaluate the effective boolean value of the expression
        Overrides:
        effectiveBooleanValue in class Expression
        Parameters:
        context - the given context for evaluation
        Returns:
        a boolean representing the result of the comparison of the two operands
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression
      • compare

        public static boolean compare​(AtomicValue v0,
                                      int op,
                                      AtomicValue v1,
                                      AtomicComparer comparer,
                                      boolean checkTypes)
                               throws XPathException
        Compare two atomic values, using a specified operator and collation
        Parameters:
        v0 - the first operand
        op - the operator, as defined by constants such as Token.FEQ or Token.FLT
        v1 - the second operand
        comparer - used to compare values. If the comparer is context-sensitive then the context must already have been bound using comparer.provideContext().
        checkTypes - set to true if it is necessary to check that the types of the arguments are comparable
        Returns:
        the result of the comparison: -1 for LT, 0 for EQ, +1 for GT
        Throws:
        XPathException - if the values are not comparable
      • evaluateItem

        public BooleanValue evaluateItem​(XPathContext context)
                                  throws XPathException
        Evaluate the expression in a given context
        Overrides:
        evaluateItem in class Expression
        Parameters:
        context - the given context for evaluation
        Returns:
        a BooleanValue representing the result of the numeric comparison of the two operands, or null representing the empty sequence
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression
      • getItemType

        public ItemType getItemType()
        Determine the data type of the expression
        Specified by:
        getItemType in class Expression
        Returns:
        Type.BOOLEAN
      • getStaticUType

        public UType getStaticUType​(UType contextItemType)
        Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.
        Overrides:
        getStaticUType in class Expression
        Parameters:
        contextItemType - the static type of the context item
        Returns:
        the static item type of the expression according to the XSLT 3.0 defined rules
      • tag

        protected java.lang.String tag()
        Description copied from class: BinaryExpression
        Get the element name used to identify this expression in exported expression format
        Overrides:
        tag in class BinaryExpression
        Returns:
        the element name used to identify this expression
      • explainExtraAttributes

        protected void explainExtraAttributes​(ExpressionPresenter out)
        Description copied from class: BinaryExpression
        Add subclass-specific attributes to the expression tree explanation. Default implementation does nothing; this is provided for subclasses to override.
        Overrides:
        explainExtraAttributes in class BinaryExpression
        Parameters:
        out - the output destination for the displayed expression tree
      • getElaborator

        public Elaborator getElaborator()
        Make an elaborator for this expression
        Overrides:
        getElaborator in class Expression
        Returns:
        a suitable elaborator